(1.) Field of the Invention
This invention relates to a process for preparing laminate polymer articles. More particularly, it relates to a process for preparing laminate polymer articles, wherein a composite acrylic film comprised of an alkyl methacrylate polymer film and a carrier film is laminated on at least one surface of a prepolymer containing a polymerizable monomer and/or a solvent, such as a fiber-reinforced unsaturated polyester (hereinafter referred to as "FRP" for brevity) prepolymer, so that the surface of the alkyl methacrylate polymer film is in contact with the prepolymer; the prepolymer is polymerized and cured; and then, the carrier film is peeled from the composite acrylic film to obtain a laminate polymer article having the alkyl methacrylate polymer film as a surface protecting layer. The present invention also relates to a composite acrylic film which is used in the above-mentioned process as a surface protecting layer for a polymer article.
(2.) Description of the Prior Art
Thermoplastic resins such as ABS resins, vinyl chloride polymer resins and polycarbonate resins are poor in the weatherability, and as is well-known, as means for improving this poor weatherability, there has been adopted a method in which an acrylic film is heat-bonded or bonded by an adhesive to the surface of a final product at the shaping step.
Plane sheets and corrugated sheets of FRP are used indoors and outdoors in large quantities as construction materials, green house materials, road materials and industrial materials, because they are excellent in the strength and have a light weight.
However, when FRP shaped articles are used outdoors for a long time, so-called "volume decrease", that is, the phenomenon in which glass fibers are exposed to the surface of the shaped article by errosion of the unsaturated polyester resin, takes place, resulting in loss of clarity and separation of the glass fibers from the FRP resin, and therefore, the reinforcing effect by the glass fibers is drastically reduced. Moreover, by long-time outdoor use, the unsaturated polyester resin per se is yellowed, and hence, in case of an uncolored transparent shaped article, the light transmittance is drastically reduced and in case of a colored shaped article, there arises discoloration or color fading which is a fatal defect in a green house material. As means for improving the weatherability of FRP shaped articles, there have been adopted a process in which a gel coat is formed on the surface of a mold and cast polymerization is carried out in this mold and a shell molding process in which acrylic resin plates are molded and cast polymerization is carried out between inner surfaces of the molded acrylic resin plates. These processes, however, are defective in that the thickness of the acrylic resin layer applied to the surface of the molded article is too large, and application of such acrylic resin layer to a plane having a broad area is economically disadvantageous and is not preferred in view of the operation environment.
As means for eliminating these disadvantages, there has been proposed a method in which a poly(vinyl fluoride) film which has been subjected to a discharge treatment is superposed and bonded on the surface of an FRP shaped article. However, this method is still not satisfactory in that bonding of the poly(vinyl fluoride) film to FRP is insufficient and the poly(vinyl fluoride) film tends to be peeled while the FRP shaped article is being used. Furthermore, there is adopted a method in which a paint having a good weatherability is coated on the surface of an FRP shaped article, but this method is low in the productivity and economically disadvantageous when this method is applied to the production of large-area, mass-production type FRP sheet-like shaped articles such as plane sheets and corrugated sheets.
By laminating or coating an acrylic film excellent in the weatherability on the surface of an FRP shaped article, the weatherability of the FRP shaped article can remarkably be improved and occurrence of the above-mentioned phenomenon of "volume decrease" and coloration, discoloration and fading of the resin per se can be prevented. However, in the continuous process for the preparation of FRP plane sheets or corrugated sheets, if an acrylic film is expanded on a carrier film, glass fibers are scattered thereon and an unsaturated polyester syrup is injected therein, the acrylic film is dissolved within several seconds by a styrene monomer contained in the syrup and is locally broken, perforated or shrunk. Moreover, since such laminate is heated at a high temperature at the molding step, the surface smoothness cannot be maintained in the film and it is impossible to uniformly bond the acrylic film only to the surface layer of the shaped article, with the result that the finished surface becomes marked with blobs and crepy and it is impossible to form a uniform surface protecting layer.